1. The Field of the Invention
The present invention relates to a method and apparatus for controlling a rotary actuated valve or the like from a remote location and in particular to a method and apparatus which controls the rotary actuated device permitting it to be set and reset with precision.
2. The Prior Art
The present invention finds use in the field of petroleum production and in particular to the servicing of gas wells located at offshore platforms. Offshore gas recovery platforms have a number of unique requirements including the ability to be rapidly shut down should the platform be threatened by an approaching weather system. Heretofore, it would have been necessary for production workers to attend to closing each of the valves on each of the production platforms. This would entail a substantial interruption in production considering the fact that the production rigs are often spaced a good distance apart and that there may be a number of valves which have to be closed with the approaching storm. A similar delay would be encountered in resetting the valves when the storm is no longer a threat. In gas recovery there are also production quotas which require the appropriate periodic resetting of the valves. Normally this would require the intervention of production personnel at each of the production platforms adjusting and resetting each of the valves manually.
There are known systems for controlling valves, but these systems are primarily of the linear type where the valve or choke is controlled by a reciprocal ram, generally acting against a spring bias tending to drive the valve or choke to a closed position. The known valve actuators of this type generally employ air or hydraulic cylinders which act against spring bias means to hold the valve or choke at the desired setting. The primary difficulty with this type of device is, should there be a failure of the hydraulic or air pressure, then the entire system will experience a shutdown. The failure of system pressure for even the briefest interval as well as failure by a drop in pressure below system tolerances can result in the unintentional and undesirable shutdown of the system. Another disadvantage of the fluid actuated systems is that they require pressurization at all times thereby necessitating that there must be a source of pressurization for the fluid.
The present invention overcomes many of the difficulties experienced with the prior art devices by providing a system which allows control of rotary actuated valves, chokes or similar control devices from a remote location and with great precision in the setting of the valve, choke or control device. A particular advantage of the present invention is that it can be added to existing production equipment without undue capital expense thereby significantly updating automation of a functioning production facility with minimal interruption of operation of the facility.